Centrifugal molding of concrete products



May '16, 394 R. J. VAN NIEKERK CENTRIFUGAL MOLDING OF CONCRETE PRODUCTSFiled Aug. 20, 1942 Jane 1. 250/ jisseZJTk Patented May 16, 1944 Russell.Iuan van Niekerk, Florida, Transvaal, Union of South Africa ApplicationAugust 20, 1942, Serial No. 455,513

' In the Union'of South Africa October 7, 1941 4 Claims.

This invention relates to the centrifugal molding of concrete products,particularly concrete poles and pipes, and the lining of pipes withconcrete, bitumen or like material.

Hitherto, in the centrifugal molding of concrete products and lining ofpipes, the initial distribution of the concrete in the mold or thelining material in the pipe has been a process occupying considerabletime or involving a considerable expense of labor. The customary methodof 'distribution has been to introduce the concrete' or liningmaterialin successive charges and to ro-' tate the mold or pipe slowly, with orwithout vibration, until the charge has become distributed along thelength of the mold or pipe. It has a1s0 been proposed to mount the moldor pipe for charging purposes in a stationary position on a beam orframe which can be tilted-so as to bring the mold or pipe to an inclinedposition with its charging end upwards, whereafter the concrete orlining material is delivered into the open end and descends down themold or pipe by gravity. This method, however, involves the subsequentprocess of bringing the beam ,or frame to the horizontal, thenremovingrthe mold or pipe therefrom and placing it in a separat machinefor spinning the mold or pipe, themachine being first rotated at arelatively slow speed so as to -com plate the "distribution" of theconcrete or lining material. j One of the: objects of the presentinvention is to facilitate and expedite the distribution-of the concreteor lining material in the mold or' pipe. A further objectis tofacilitate the spinning'of the mold or pipe in a manner best calculatedto ensure the" consolidation of the concrete or lip.- ing material in auniform,man ner throughout the product or lining to be formed.

A, still further object is to enable hollow poles, pipes or likeproductsto be spun with a-wallof substantially the same thickness throughout thelength thereof, or with a wallvaryingin'thickness in a predeterminedmanner and degree. In particular, it is an'object of th invention'toenable'tapered hollow poles, pipesjand like tapered products to be spunwith a-wall of uniform thickness throughout, 1. 'e., with-a taperedexternal surface and an internal surface tapered similarly-,thus'avoiding" wastage of material and effectin a-savmgjm w ei htof theproduct,jas Com -j pared with tapered hollow products manufacturedhithertii, n which the bore or inte na surface is cylindrical 1 orparallel, or at any=rate not tapered inia greementiwiththe external tae: 'of the wall; and the thickness bf th wauat the wider end of theproduct consequently in excess of what is required'for purposes ofstrength.

Another object of the invention is to provide a simple and inexpensivemachine for distributing and spinning the concrete or lining material.

According to this invention, I provide a method of centrifugally moldingconcrete products or centrifugally linning pipes in which the mold orpipe, during the charging of theconcrete or lining material, isrotatably supported in an inclined position and is rotated in thisposition so as to distribute the concrete or lining material along andwithin the pipe by a combined gravity and rotational action.

In accordance with a further feature of the invention, the method issuch that the mold or pipe, when the concrete or material has beenproperly distributed therein, is spun at any desired speed, while lyingat any desired inclination, so as to consolidate the concrete or lininmaterial by centrifugal force, While still keeping non-consolidatedconcrete or lining material under the combined control of thecentrifugal force and-gravity.

According to another feature of the invention, a machine forcentrifugally molding concrete products and lining pipes comprises meanswhereby the mold or pipe is rotatably supported and whereby it is, whileso supported, variable in inclination, and means for rotating orspinning the mold or pipe at any given inclination at different speeds.V

The invention will now be described, by way of example, with referenceto theannexed drawing, in which- Fig. 1 is a View in side elevation of amachine embodying the invention and showing a mold therein;

Fig. 2 is a plan view of the machine shown in Fig.1 without the mold;

Fig. 3 is a relatively enlarged view of part of themachine shown inFigs. 1 and 2.

Referring to the drawing:

The machine comprises a beam 1 (e. g. con

sisting of a pair of plate girders suitably braced) which is pivotallymounted on a trunnion bearing'or fulcrum 2, which in the'caseillustrated is offset a distance'from the middle of'the beam towards theright-hand end. The fulcrum '2 is supported in a bearing block or blocks3 which is or are mounted on a foundation or floor 4 in which a well 5is formed in order to permit the beam to be tilted to any angle within agiven range. The beam l is' provided towards the end thereof remotefromthe' fulcrum 2 with a transverse bar Ii, over the ends of which areadapted to be fitted rings 1 provided on the ends of chains 8 which areconnected to an electric crane, hydraulic jack or other suitable means(not shown) for the purpose of raising and lowering the beam I to theparticular inclination desired, e. g., the position shown in dottedlines in Fig. 1.

At intervals alongthe beam I, pairs of supporting rollers 9, ID aremounted on bearing brackets II. The drive of an electric motor I2mounted on the beam I is transmitted by means of belt or other gearingI3 to one of the pair of supporting rollers, vig. the pair of rollers 9,III above the fulcrum 2.

In Fig. 1, a tapered mold I4 made-in two halves is shown mounted in themachine. This/par ticular mold is one adapted for: the 1 centrifugalmolding of a tapered reinforced concrete pole. It is fitted with areinforcement positioning device comprising a clamp or holder I5 at oneend of the mold, and a positioning plate or element IS, a secondclam-por holder I'l, and a screwtensioning meansI8 at the other'endofthe mold,-all as specified in my. co-pending applicationNo. 455,514.

On the mold I4, spinning rings I9 are provided at the same intervalsapart as the pairs of supporting rollers 9, I0. These rings are fixedrigily and coaxially upon the mold I4 and rest, and are adapted'to roll,upon the rollers 9, I0. Thus, on the electric motor I2 being set inoperation, the rollers 9, lfl'driven by the belt or other gearing I3cause rotation of the mold I4 about its axis, the speed of this rotationbeing varied by variation of the speed of the motor.

As indicated in Fig.3, a displaceable jockeyroller carried by a bent-armlever 2I is associated with each pair of supporting rollers 9, III. Thisjocket-roller 20 is adapted to be brought into rolling contact with thetop of the corresponding spinning ring I9 and to be held in such contactwith a greater or smaller degree of pressure by an adjustment nut orhandle 22 which is turnable on the screw-threadedend 23 of a retaininglever 24. In this manner, the mold I4 is retained on the rollers 9, I0during spinning, and-chattering or undue vibration of the moldisavolded.

In order to prevent lengthwise movement of the mold I4, the end spinningrings I9 are formed with double flanges 25, 26 and the intermediatespinning rings I9 are formed with single flanges 21, the side surfacesofthe flanges 25, 26 and 21 being adapted to take up end-thrust bycontact with the corresponding side surfaces of 'the respectivesupporting rollers 9, III.

The end of the beam I remote from the fulcrum 2 may be termed thecharging end ofthe machine, and is fitted with a charging hopper 28, themouth or forward part 28 of which is tapered and adapted to project ashort distance into the adjacent end of the mold I4. The mold I4 (or thepipe, as the case may be) is placed in the machine so that its largerend is the end into which the concrete (or lining material) is charged.This end is the end which is elevated when the beam I is tilted. For thepurpose of charging the concrete into the mold from the hopper 28, thereinforcement clamp or holder I5 is made of annular shape so as toprovide the necessary opening through which the concrete may enter themold.

The method of molding (or lining) with the machine described is asfollows: 1

The beam 1 is set in a horizontal position in order to receive the moldI4, this latter, in the particular case described, having previously hadthe reinforcing wires (parts of which are indicated diagrammatically bydotted lines 29 in Fig. 1) positioned therein by the positioning devicesI5 to I8 already referred to.

The mold I4 is placed so that the spinning rings I9 rest upon thesupporting rollers 9, I0 and is retained in this position by bringingover on top of the spinning rings I9 the jockey-rollers 20, and securingthem in place by the handles 22 andscrew-threaded levers 24.

The hopper 28 is charged with the quantity of concrete required, and theelectric crane or other hoisting means (not shown) connected by thechains "8 and rings 1 to the transverse bar 6 is operated so as to-tiltthe beam I and mold I4 thereon toafai-rly substantial inclination, suchas the position shown in Fig. 1 in dotted lines. In this position, theelectric motor I2 is switched onso as to set themold I4 rotatingslowly,andthe concrete in .the hopper. 28- is charged into the large endof the mold. By virtueof therotation, and inclinationof the mold, theconcrete is distributed around its interior.

When this preliminary distribution is complete, the beam I'isloweredfromthe dottedposition (Fig. 1) to the level or'to an inclinationsuitable for high-speed. spinning, i. .e. for consolidating the poleor-other product "by centrifuging. In the case of a-cylindrical orparallelsided product, this level will be the horizontal position asshown in full lines in Fig, 1.

reinforced-concrete pole particularly described above), theinclination-will be at an angle approximating tothe horizontal, butconsiderably less than theang-le of the beam shown in dotted lines inFig; 1. More specifically, the inclination is necessarily such that theeffect, during centrifuging, of the taper of the mold (viz. to'causecreeping of the centrifuged concrete from the smaller to thelarger endofthe mold) will be counteracted by thegravitational-effect onthe concreteproduced by the inclination of the-mold. These two opposing .efiec-tsbeing balanced-the concrete during centrifuging will be subjected purelyto a centrifugal or radical consolidation, and the original-uniformityof distribution of the concrete in the mold will not be distunbed,-and aproductwith a uniformly thick wall, with'its internal and externalsurfaces tapered: alike, will be obtainable.

Thus during centrifuging, the whole or the concrete,includingiconcrete-not yet consolidated; is under the combined controlof centrifugal force and gravity, .in such a mannerv as to-makeepossiblewhatever distribution and-consolidation of concrete is desired.

When .moldingor consolidation of the product is complete, rotation ofthemold I.4--is stopped by switchingofithemotor I2. Thereaftent mold andbeam lare lowered to "the horizontal position, the handles. 22'are.unscrewed,-.the levers 2| carrying the jockey-rollers '20'swungmback, and I the mold removed 7 from the machine, for eventualwithdrawal therefrom-of the 'molded product.

As wilirbeappreciatedthe inclination ofthe mold, and itsspeed-ofrotation, may both be varied at will inthecourse.cf-thedistributingIand/or centrifuging operations, without thenecessity of stopping,--or in any- :wa-y interfering-with, the work. Thmold (or therpipeiinthe case-orig pipe'being. centrifugally lined) 1salwaysunder In the, case of a tapered product (suchas the taperedcomplete control, so that any tendency towards lengthwise creeping ofthe concrete (or linin material), or incorrect rate or degree ofconsolidation at one end or another of the mold (or pipe) canimmediately be rectified.

While the method of operation has been particularly described withreference to the molding of a tapered reinforced-concrete pole, it willbe obvious from the indications already given that the machine may alsobe used for molding parallel or cylindrical poles and tapered orparallel hollow bodies or pipes, and for the centrifugal lining ofhollow bodies or pipes.

Various modifications may be made in the machine described, withoutdeparting from the scope of the invention. For example, instead ofretaining the spun body on the supporting rollers 9, II] by means ofjockey-rollers 20, I may employ for this purpose endless belts orequivalent means.

In the appended claims, the term centrifuging is intended to includecentrifugally molding concrete products and centrifugally lining pipes,the term hollow body is intended to include a mold to be charged withconcrete and a pipe to be charged with lining material, and the termmaterial is intended to include the concrete or lining material.

I claim:

1. A method of molding a hollow tapering concrete product, consisting ininclining and slowly rotating an appropriate mold with its larger enduppermost while charging the same with material, and then subjecting themold and material to a rapid rotation while maintaining the inclinationof the mold at a degree to cause an incident gravital influence on thematerial sufiicient to overcome the tendency of the material to creeptoward the larger end of the mold under the centrifugal operation.

2. A method of molding a tapering concrete product to produce an articlehaving substantially even wall thickness throughout, consisting inslowly rotating a tapered mold while steeply inclined downwardly fromits larger end, feeding the material into the larger end anddistributing such material throughout the mold through such rotation andinitial inclination, then materially increasing the rotation whilevarying the inclination to a degree to develop a gravital influence onthe material to overcome the tendency of the material to creep under thecentrifugal influence, whereby to insure a wall of substantially uniformthickness throughout.

3. A method of molding hollow concrete products of tapered form withsubstantially uniform wall thickness throughout, consisting in mountingan appropriate mold for pivotal and rotative movement, inclining themold with the larger end uppermost and slowly rotating to insuregravital feed and rotative spread of the material, feeding the materialonto the mold, and then rotating the mold to develop centrifugal actionfor increasing the rapidity of setting of the material while at the sametime arranging the inclination of the mold at a degree to influence thematerial by gravity to overcome the tendency of the material to creeptoward the larger end of the mold incident to the cetrifugal influence.

4. A method of molding hollow tapered concrete products withsubstantially uniform wall thickness, consisting in inclining the moldfor gravital feed of the material lengthwith the same, placing thematerial in the mold, and rotating the mold at a relatively slow speedfor distributing the material, and then rotating the mold at arelatively high speed for centrifugal placement and to increase therapidity of setting of the material while maintaining the mold at apredetermined inclination to develop a gravital influence to counteractcreeping influence of the material under centrifugal action.

RUSSELL JUAN VAN NIEKERK.

